The objective of the proposed research is to use nuclear magnetic resonance spectroscopy to obtain information about the structure and function of a variety of respiratory proteins in solution. The work will involve the development of new sensitive NMR methods which could be of widespread use in both biology and chemistry. First we will construct a versatile, sensitive, high-field, superheterodyne pulse spectrometer utilizing a 3 1/2 inch bore superconducting solenoid. We then propose to construct a 40 mm spinning sample probe for high-resolution NMR spectroscopy of carbon-13 and nitrogen-15. A second development is that of a cryogenic probe and preamplifier for high-resolution work: increased signal-to-noise ratios will be obtained because of decreased Nyquist noise. A third development is that of a coaxial or stripline resonant cavity probe, based on a quarter-wave capacitively loaded circuit, for high-frequency NMR. We will study ligand induced conformational transitions in hemoglobin in intact erythrocytes as well as studying the structures of various cytochromes and flavodoxins in solution, by C-13 and N-15 NMR. We are interested in elucidating the nature of "R-T" transitions in hemoglobin, and propose use of mutant, chemically modified, isotopically enriched and paramagnetically labelled hemoglobin species in this project. With the cytochromes, we are particularly interested in which groups constitute the oxidase and reductase binding sites - as a suitable first step in determining the mechanism of electron transfer with cytochrome c. We propose preliminary experiments with flavodoxin, a small, readily produced member of the important flavoprotein class, aimed at determining the structure of this species in solution. We propose a number of experiments using nitrogen-15 NMR, designed to test the likely usefulness of this isotope in biological NMR research.